This invention relates to an improved grouting method for grouting the annulus between either a jacket leg or pile sleeve and a pile driven therethrough or any similar annular shape of an offshore platform used in well drilling and production.
The prior art teaches several different methods of grouting the annular space formed between either a jacket leg or pile sleeve and a pile driven therethrough of offshore platforms. Typically, the methods involve setting a grout plug or column of grout which is supported either by the bottom of the body of water upon which the platform is installed or on a grout seal and subsequently filling the annular space above the plug with grouting material. Such typical prior art grouting methods are illustrated in U.S. Pat. Nos. Re. 28,232, 3,468,132, 3,878,687, 4,009,581, 4,047,391, 4,052,861, 4,063,421, 4,063,427, 4,077,224, 4,140,426, 4,171,923 and 4,275,974.
However, should such a grout plug or column not be supported by either a grout seal or bottom of the body of water, the grout will merely run out the bottom of the annular space into the surrounding water or area. Also, if some way of sealing the annulus cannot be found so that a grout plug or column can be placed in the annulus and allowed to harden, the annulus cannot be filled with grouting thereby affecting the stability of the offshore platform.
Previously, when trying to seal the annular space a wide variety of materials have been used. Typically, fast setting gypsum cements have been tried, lost circulation materials used in well drilling have been tried, etc. In some instances where the annular space is accessible, divers have sealed or tried to seal the annular space by filling it from the bottom with sacks, rags, rubber materials, etc.
However, the use of fast setting gypsum cements plug up flow lines, lost circulation materials used in well drilling operations have not proven satisfactory since they are usually not capable of bridging large open areas, and the use of divers is expensive.
To consolidate the surface of a borehole in an incompetent formation and strengthen the bond between the surface of the borehole and cement placed therein the prior art teaches the method of forcing a multivalent cation salt into the formation, thereafter forcing an alkali metal silicate solution which has a pH less than 12.0 containing at least 12% by weight silica into the formation, and thereafter forcing an aqueous cement slurry containing at least 2% by weight of a water soluable multivalent cation salt to contact the surface of the borehole. Such a prior art method is disclosed in U.S. Pat. No. 4,1014,174.